slow startup computer, mouse non-responsive

Help please! looking for hidden problems.
Computer is about a year old, has recently started running slower. Takes a while to startup - much more than it used to. Yesterday, the mouse (kind with the mini DIN plug) froze on startup and won't respond (?). This is something new. I tried a different mouse with no results. Plugged a USB mouse in and it works ok - not sure if this is a hardware problem or what. Starting in safe mode doesn't change the non-functioning of the serial mouse.
Ran/run norton antivirus 2005 - no problems found. Also ran Avast antivirus with no results. Ran adaware SE and spybot, and cleaned up what it found, but still wonder if there is more in there hiding. Has been defragged as well.

did you reboot after you plugged in that other mouse?
PS/2 plug devices (which your mouse is) won't usually work until the power has been interrupted on the bus.

If you have you either have 2 bad mice or you may have a faulty PS/2 bus or controller.
As you can use USB or (if you still have a serial port) serial rodents it's not much of a problem, more of an annoyance.